This invention relates to a sensor arrangment for a sensor having a differential output. The arrangement is particularly although not exclusively useful for pressure sensors.
Pressure sensor elements are known to suffer from two major variations namely device to device variations and temperature effects.
Device variations take the form of an offset, which is the voltage output of the sensor for zero applied pressure, which offset differs for different devices, and a variation in the full scale output of the device.
Temperature variations influence both the offset and the full scale of pressure sensors. In respect of the offset the entire output voltage versus pressure characteristic is shifted whilst the effect of temperature changes on the full scale is to change the slope of the characteristic.
It is usual to use an operational amplifier to increase the amplitude of the pressure sensor signal. Such amplifiers themselves introduce errors such as input voltage and current offsets and an input bias current which develop an output voltage offset.
In order to compensate for these amplifier voltage offsets for absolute value and temperature variations it is necessary to utilize precision dedicated operational amplifiers with an extensive calibration procedure, which must be carried out for each sensor-amplifier unit. This procedure can be the most expensive part of the manufacturing process.
This invention seeks to provide an improved sensor arrangement in which the above mentioned problem is mitigated.